1. Field of the Invention
The present invention relates to an imaging device that generates and displays a focusing confirmation image for focusing confirmation and a control method thereof.
2. Description of the Related Art
There is a digital camera including a so-called manual focus mode in which the user can manually perform focus adjustment, besides automatic focus using a phase difference detection system or the like described in PTLs 1 and 2, for example. Further, there is known a digital camera that displays a split image in a live view image (which is also called a through image) to facilitate work that a photographer performs focusing on an object at the time of this manual focus mode (see PTLs 3 and 4).
The split image is vertically divided, the upper and lower images of the split image are horizontally shifted at the time of defocus, and the upper and lower images are not horizontally shifted in a focus state. By this means, the photographer can perform focusing by performing focus operation such that the upper and lower images of the split image are not horizontally shifted.
As illustrated in FIG. 26, a digital camera that can display a split image includes a color imaging element 100 in which normal pixels for photographing (whose illustration is omitted) and two kinds of phase difference pixels G1 and G2 that receive pupil-divided object light are two-dimensionally arrayed on the imaging surface. On this imaging surface, a pair of sequence patterns Q3 having first array pattern Q1 and second array pattern Q2 in which phase difference pixels G1 and G2 are arrayed at regular intervals in the horizontal direction respectively are arrayed at regular intervals in the vertical direction. The digital camera having the color imaging element 100 generates a photographing image on the basis of an output signal from the normal pixel and performs live view image display while generating a split image on the basis of respective output signals (pixel values) of two kinds of phase difference pixels and performing display in a live view image.
However, in the color imaging element 100, phase difference pixels G1 and G2 are disposed in the same pixel line in the vertical direction respectively but phase difference pixels G1 and G2 are not disposed in the same pixel line in the horizontal direction. Therefore, in a case where the color imaging element 100 takes an image of a horizontal high-frequency object as illustrated in FIGS. 27A and 27B, the boundary and gap between upper and lower images of a split image are clearly displayed. Meanwhile, in a case where the color imaging element 100 takes an image of a vertical high-frequency object as illustrated in FIGS. 28A and 28B, since the boundary and gap between upper and lower images of a split image are not clearly displayed, there is a risk that the focusing accuracy decreases.
Therefore, as illustrated in FIG. 29 and FIG. 30, in a color imaging element 102 described in PTLs 3 and 4, one of phase difference pixels G1 and G2 is disposed in a W-shaped manner on the imaging surface and the other is disposed in an M-shaped manner. By this means, phase difference pixels G1 and G2 are disposed in the same pixel line in the vertical direction respectively and also disposed in the same pixel line in the horizontal direction.
When a split image is generated on the basis of output signals of phase difference pixels G1 and G2 of such array patterns, it is general to generate the split image with an assumption that the pixel arrays of phase difference pixels G1 and G2 are linear arrays as illustrated in FIG. 26. In this case, a pixel located between phase difference pixels G1 is assumed to be interpolation pixel g1, and the pixel value of this interpolation pixel g1 is calculated by pixel interpolation according to arrows VT and VB. Moreover, the pixel value of interpolation pixel g2 located between phase difference pixels G2 is calculated by pixel interpolation according to arrows VT and VB. Further, the split image is generated on the basis of the pixel values of respective phase difference pixels G1 and G2 and the pixel values of interpolation pixels g1 and g2.
Moreover, as shown by arrows VT and VB, there is also a method of performing interpolation processing by the use of the pixel values of phase difference pixels G1 and G2 located on the left side and right side of interpolation pixels g1 and g2 in the figure instead of performing interpolation processing by the use of the pixel values of phase difference pixels G1 and G2 located on the upper side and lower side of interpolation pixels g1 and g2 in the figure. That is, the pixel values of interpolation pixels g1 and g2 are calculated by performing pixel interpolation according to arrows VR and VL respectively. Even in this case, a split image is generated on the basis of the pixel values of respective phase difference pixels G1 and G2 and the pixel values of interpolation pixels g1 and g2.
Since phase difference pixels G1 and G2 are disposed in the same pixel lines in the vertical direction and horizontal direction in the color imaging element 102, when a vertical high-frequency object is imaged, the boundary and gap between upper and lower images of a split image are displayed more clearly than when it is imaged by the above-mentioned color imaging element 100. As a result, it is possible to improve the focusing accuracy more than a case where the color imaging element is used.